If by "suicide trap" you mean it's completely inescapable once you're in it, my answer is the secret flamethrower room on "Smells Like Napalm, Tastes Like Chicken!" accessible by stepping on a platform trigger down "Tunnel System #A894C", then dashing back to the starting room and riding the platform down. After a short time, the platform will rise, trapping you inside if you're not fast enough.
There's also the "Deprivation Chamber" on the earlier level "Never Burn Money", leading to the Gheritt White terminal, but you can escape that if you know how.
Either way, escape involves grenades. ;)
In M1A1, the first suicide trap is on "Arrival". The trap room is the ammo room outlooking "Hangar 7A (Port)", reachable from the second half of the ventilation shaft maze. After entering the room, you can activate the platform that brought you down and step off quickly, trapping you. This was so in the demo version I believe, remember the secret Bob room from the demo is also present.
